ROLE OF STATIC DEFORMATION AND COMPACT ORIENTATION OF TARGET NUCLEUS IN MEASURED FUSION, FUSION-FISSION AND CAPTURE CROSS-SECTIONS OF Pu-244+Ca-48 REACTION

摘要

The dynamical cluster-decay model (DCM), with deformations and orientation degrees of freedom of the incoming nuclei and of outging fragments included, is used to study the excitation functions of the "equatorial" compact hot fusion reaction Pu-244+Ca-48->(292)114*(compact orientation angle theta(c)=90 degrees for Pu-244).Considering the higher multipole deformations up to hexadecapole deformation beta(4)and configurations with "compact" orientation theta(c),the model is shown to give a good description of the measured individual light-particle decay channels sigma(xn),here x=3,4 and 5, and other decay channels,the fusion-fission sigma(ff)and quasi-fission sigma(qf)(equivalently, capture sigma(cap))within one parameter fitting, the neck length Delta R.The quasi-fission is also considered as a cold process with an elongated "polar" configuration.The xn-channel cross-sections for collisions between nuclei with static deformations at their respective compact orientations are shown to be much more than for the case of the nuclei taken to be spherical, signifying the increase in fusion threshold for an intermediate hot fusion reaction to be associated with the static deformation of the target nucleus and its orientation at the point of collision in its path toward the (spherical)compound nucleus. The shell effects in both the potential and kinetic energy(the mass parameters)terms of the Hamiltonian are shown to be important. The free parameter Delta R of the model is shown to depend strongly on limiting angular momentum, which in turn depends on the use of sticking or non-sticking moment of inertia for angular momentum effects. For the sticking moment of inertia, the evaporation residue (neutron emission)is shown to occur almost promptly largest Delta R), followed by the competing (hot/cold) quasi-fission and ending finally with fusion-fission of hot compound nucleus. Different Delta R's(equivalently, relative separations) for the three processes means to predict that the processes ER,ff and qf happen in different time-scales, in agreement with the indications of experiments.